The reaction to Hugo Lloris's unconfirmed second or two of unconsciousness after his headfirst collision with Romelu Lukaku's knee last weekend was a curious – and possibly game-changing – chapter in the continuing phone-in of our sporting lives. Even by the standards of crowd-sourced controversy, the response to the Spurs goalkeeper's insistence on continuing to play despite feeling a bit groggy looked more exaggerated than an Ashley Young dive. After all, which footballer, or rugby player (not to mention boxer) has not come round from momentary disorientation and, after sorting out the days of the week and the name of the current prime minister, returned to the fray? How would AP McCoy have ever got his 4,000 winners had he not many times got knocked down, and got back up again? Weren't many of the legends of our sporting past – Brian Close heading away Michael Holding bouncers, Terry Butcher with his Halloween bandage – forged from minor concussion, heart ruling head …

At least that was the instinctive argument. But, as has been shown this week, it is one that ignores two distinct realities that are changing the way we watch and play contact sport. The first is the advance of medical science, which gives ever greater insight into the measurement of physical harm and related risks. Nowhere is this ability more marked than in the multi-coloured brain scans of neuroscience. Lloris's own brain was not available for public dissection, but images of others were produced in evidence to support the unarguable wisdom that any instance of concussion should be treated with great caution.

A second reality that the goalkeeper's courage or foolishness highlighted, however, mostly remained unspoken, though you could perhaps detect it in the unusually speedy response from Fifa in condemning the medical team at Spurs. That reality is the growing climate of litigation in professional sport. In Fifa's criticism of André Villas-Boas's "irresponsible" judgment that Lloris had shown "great character and personality" by playing on, you could hear echoes of a recent landmark American agreement concerning head injuries in the National Football League, one that has been seen to threaten the entire future of that sport.

In August, after years of denial, the NFL agreed to a $765m (£478) out-of-court settlement with a group of former players who had sued the league for its role in hiding or underplaying the effects of brain trauma in the game, while glorifying its violence, a cover-up which has been exposed in a series of recent books and documentaries. Individual former players suffering motor neurone disease, for example, will as a result be entitled to payouts of up to $5m. If a further test case judgment is approved by a federal judge in the coming months all former players with conditions ranging from depression to Alzheimer's may be eligible for compensation.

The story is rooted in a study of the brain of a former Philadelphia Eagles player, Andre Waters, who in December 2006 took his own life. The neurologists who looked at Waters' brain described its 44-year-old tissue as resembling that of an 85-year-old Alzheimer's patient, and made the link to his career, a finding which prompted the New York Times to give space to the argument that parents should "not send their children back out on to the fields". Since then, many former NFL and college players have been tempted to the courts. There have been 3,500 cases brought by former professional gridiron players in California alone, a number which has led governor Jerry Brown to endorse legislation to prevent such litigation in the state.

If the financial implications of such cases are potentially enormous so the risks associated with playing sport are increasingly being interrogated. One positive outcome is a much greater emphasis on safe technique in the junior levels of all sports. Another, more contentious trend is the spread of legal claims to other injuries and other sports. In America "soccer" players are increasingly seeking compensation not only for the lasting effects of head injury but also for long-term damage to hips and knees and ankles. The former World Cup player Eric Wynalda, for example, recently won a $127,500 settlement from Chicago Fire of the MLS for a range of injuries sustained in his career. It is likely to be only a matter of time before many former players start to look at their replaced hips and the knees that won't get them upstairs and start making calls to their lawyers.

The overt concern of Fifa for Hugo Lloris might be viewed as a pre-emptive strike by the international governing body in this respect.

Definitive links between a career in professional football and later brain illness are not proven in this country though there is a good deal of anecdotal evidence to suggest that the centre-halves and centre-forwards of the 1950s and 1960s who headed thousands of sodden leather footballs for a living might be more prone to early onset Alzheimer's than most. The coroner's report into the death at 59 of Jeff Astle, the former West Brom and England forward, made the connection explicit, calling his fatal degenerative brain disease "death by industrial injury".

It is, obviously, crucial that such risks are minimised in all sports. But there is also a related danger that, with increased litigation, pitches and playing fields begin to be viewed by parents and players and governing bodies as arenas for physical harm rather than physical education. Every morning my own stiff right ankle, clicking left knee and rebuilt shoulder remind me that I used to love playing football – I can well remember the collisions, mostly mistimed on my part, that first caused all three. Was I aware of the risks at the time? Probably not.

Would I – along with any other 18-year-old – have played anyway had I known how I would feel on cold mornings aged 47? Of course.